A facile method to introduce a donor-acceptor system into polymeric carbon nitride for efficient photocatalytic overall water splitting

It is a prospective strategy to produce sustainable energy by photocatalytic overall water splitting (POWS). This work aims to develop a simple method for integrating a donor-acceptor system into polymeric carbon nitride (PCN) structure, which could accelerate the charge separation significantly. In the as-prepared photocatalyst (COCNT), carbon and oxygen were successfully incorporated into the framework of PCN, and the chemical environment of C and O was well probed by X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS). It showed that the C-containing and O-containing segments of COCNT played the role of a donor, while the heptazine part played the role of an acceptor. In addition, Density-functional-theory (DFT) calculations confirmed the spatial split of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for promoting charge separation. Impressively, COCNT could efficiently split pure water to generate hydrogen and oxygen. And, the photocatalytic hydrogen evolution rate over COCNT (1550.9 µmol g–1 h–1) is about 17-fold higher than that of PCN. Finally, we proposed a possible photocatalytic mechanism to explain the above results.